Modern aircraft often use a variety of high lift leading and trailing edge devices to improve high angle of attack performance during various phases of flight, for example, takeoff and landing. One such device is a trailing edge flap. Current trailing edge flaps generally have a stowed position in which the flap forms a portion of a trailing edge of a wing, and one or more deployed positions in which the flap extends forward and down to increase the camber and/or plan form area of the wing. The stowed position is generally associated with low drag at low angles of attack and can be suitable for cruise and other low angle of attack operations. The extended position(s) is/are generally associated with improved air flow characteristics over the aircraft's wing at higher angles of attack.
Proper extension and retraction of such flaps is important for control of the aircraft during different maneuvers. As such, it is conventional to include multiple feedback systems to monitor flap deployment and retraction. For example, sensor systems may monitor absolute flap position, flap skew position and detection of a jam or disconnected actuator.
In general, such systems can include a control unit that causes a main drive unit to produce rotation of a shaft. This rotation can then be converted to flap extension in known manners such as by use of a ball screw. In such systems, each flap typically includes two actuators, one for each side of the flap. If the two actuators do not extend two sides of the flap the same amount, the flap experiences skew. Further, in some cases, the actuator may not be working effectively and determination of such, as well as skew, may be beneficial.